CO ADSORPTION ON CU3PT(111) - A LEIS STUDY

The interaction of CO with the Cu3Pt(111) surface has been studied by low energy He+ ion scattering. The intensities of He+ ions scattered o ff O, Cu and Pt were only detected, indicating the orientation of the CO molecule with O facing away from the surface. In the initial stages of CO adsorption at 200 K, the Pt intensity in a Cu-enriched surface was not detectable at an exposure of 6 L CO. This was interpreted as a preferential chemisorption of CO onto Pt sites. At a saturation cover age of CO, however, the Pt intensity in a Pt-enriched surface fell to similar to 15% of its clean surface intensity, indicating not all the Pt sites were covered by the CO molecules. The results also suggested that the presence of the CO adsorbed surface layer does not induce sur face segregation of Pt. The distance between the adsorbed CO along the [0 $($) over bar$$ 11] azimuth below a saturation of CO coverage has also been tested.